Devices, systems, and methods for instillation of foamed fluid with negative pressure wound therapy

ABSTRACT

Systems and methods for delivering a foamed fluid to a wound of a patient (e.g., through a wound dressing covering the wound and coupled to the skin around the wound).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.13/009,630, filed Jan. 19, 2011, which claims the benefit, under 35 USC119(e), of the filing of U.S. Provisional Patent Application No.61/297,471, entitled “Devices, Systems, and Methods for Instillation ofFoamed Fluid with Negative Pressure Wound Therapy,” filed Jan. 22, 2010,which is incorporated herein by reference for all purposes.

BACKGROUND 1. Field of the Invention

The present invention relates generally to healing of wounds andwound-treatment therapies. More particularly, but not by way oflimitation, the present invention relates to systems and methods forimproving fluid-instillation and negative pressure wound therapy (NPWT)apparatuses and methods.

2. Background Information

Clinical studies and practice have shown that providing a reducedpressure in proximity to a tissue site augments and accelerates thegrowth of new tissue at the tissue site. The applications of thisphenomenon are numerous, but application of reduced pressure has beenparticularly successful in treating wounds. This treatment (frequentlyreferred to in the medical community as “negative pressure woundtherapy,” “reduced pressure therapy,” or “vacuum therapy”) provides anumber of benefits, including faster healing and increased formulationof granulation tissue. Typically, reduced pressure is applied to tissuethrough a porous pad or other manifold device. The porous pad containscells or pores that are capable of distributing reduced pressure to thetissue and channeling fluids that are drawn from the tissue. The porouspad may be incorporated into a dressing having other components thatfacilitate treatment

Typical instillation therapy instills fluid into a wound under a lowpositive pressure. For maximum therapeutic effect, the instilled fluidshould reach all exposed tissue surfaces. The practice of fully fillinga wound with instillation fluid, combined with the application of porouswound fillers and negative pressure to help distribute fluid, aretechniques used to try an achieve good instillation therapy. Suchtechniques include numerous disadvantages. For example, filling a woundwith fluid is wasteful, particularly where expensive fluids (e.g.antibiotics) are used as the bulk of the fluid enters the dressing(e.g., a foam) to enable the surface of the wound to be ‘coated’ withinstillation fluid.

Even where the instilled fluid is inexpensive, large volumes of fluidmay be involved, requiring frequent canister changes that may lead touser dissatisfaction. Although low positive pressures are typically usedto fill the wound cavity, the hydraulic (essentially incompressible)nature of the fluid means that over filling can quickly cause drapeleakage. Tortuous contours within a wound cavity may be difficult toreach with both foam dressings and liquid-fill techniques as gas pocketsmay be created. Applying a low vacuum during liquid instillation (tohelp maintain a seal and reduce leaking, to minimize patient discomfort,and to aid fluid distribution) can be problematic as instilled fluid maybe removed before it is fully distributed through the dressing.

For at least the reasons described above, improved wound treatmentsystems and methods are therefore desired.

SUMMARY

The present disclosure includes embodiments of wound-treatment systems,wound fillers, and methods.

Some embodiments of the present wound-treatment apparatuses (e.g., forthe treatment of wounds using negative pressure wound therapy) comprise:a drape for securing to the skin of a patient around a wound, therebycreating a space between the wound and the drape; a vacuum source influid communication with the space between the wound and the drape forapplying a negative pressure to that space; and a source of foamed fluidin fluid communication with the space between the wound and the drapefor applying the foamed fluid to the wound. Some embodiments furthercomprise a wound filler for positioning on the wound in the spacebetween the wound and the drape. In some embodiments, the source offoamed fluid generates the foamed fluid by mixing first and secondfluids (e.g., liquids). In some embodiments, the mixing is performed bycombining the first and second fluids in a single conduit. In someembodiments, the mixing is performed by combining the first and secondfluids in the space between the wound and the drape. In someembodiments, the first fluid (e.g., liquid) is an acidic solution andthe second fluid (e.g., liquid) is a basic solution. In someembodiments, the first fluid (e.g., liquid) comprises at least one ofcitric acid, acetic acid, hypochlorous acid, ascorbic acid, and benzoicacid. In some embodiments, the second fluid (e.g., liquid) comprises atleast one of a bicarbonate solution, sodium bicarbonate, hydrogenperoxide, carbonic acid, and potassium bicarbonate. In some embodiments,the source of foamed fluid generates the foamed fluid by mechanicalagitation of a liquid. In some embodiments, the source of foamed fluidgenerates the foamed fluid by injecting gas into a liquid.

Some embodiments of the present wound-treatment apparatuses comprise: adrape for securing to the skin of a patient around a wound, therebycreating a space between the wound and the drape; a wound filler forplacement on the wound in the space between the wound and the drape; avacuum source in fluid communication with the space between the woundand the drape for applying a negative pressure to that space; and asource of liquid in fluid communication with the space between thewound; where the wound filler comprises a foaming agent for forming afoam when liquid from the liquid source contacts the foaming agent. Insome embodiments, the foaming agent comprises one or more ingredientsselected from the group consisting of: sodium bicarbonate, hydrogenperoxide, carbonic acid, and potassium bicarbonate.

Certain exemplary embodiments include a wound treatment methodcomprising: delivering a foamed fluid to a wound of a patient through awound dressing covering the wound and coupled to skin around the wound.Particular embodiments comprise combining a first fluid (e.g., liquid)and a second fluid (e.g., liquid) to generate the foamed fluid. Incertain embodiments, the first fluid (e.g., liquid) comprises an acidicsolution, and the second fluid (e.g., liquid) comprises a basicsolution. In particular embodiments, at least one of the first fluid(e.g., liquid) and the second fluid (e.g., liquid) comprises asurfactant configured to stabilize the foamed fluid. The first fluid(e.g., liquid) may comprise one or more ingredients selected from thegroup consisting of: citric acid, acetic acid, hypochlorous acid,ascorbic acid, benzoic acid, saline, and lactated Ringer's solution. Thesecond fluid (e.g., liquid) may comprise one or more ingredientsselected from the group consisting of: sodium bicarbonate, carbonicacid, sodium citrate, potassium citrate, potassium bicarbonate,potassium sulfate, disodium phosphate, and sodium hypochlorite. Inparticular embodiments, combining the first fluid (e.g., liquid) and thesecond fluid (e.g., liquid) comprises activating a first fluid source todeliver the first fluid and activating a second fluid source to deliverthe second fluid.

In certain embodiments, the first fluid (e.g., liquid) and second fluid(e.g., liquid) are delivered to a combiner fitting to combine the firstfluid and the second fluid to generate the foamed fluid prior to thefoamed fluid being delivered to the wound dressing. In particularembodiments, the first fluid (e.g., liquid) and the second fluid (e.g.,liquid) are delivered to the wound dressing such that the first fluidand the second fluid combine to generate the foamed fluid in the wounddressing.

Exemplary embodiments may include: activating a fluid source to delivera fluid (e.g., liquid) to a foaming mechanism; and activating a foamingmechanism to foam the first fluid to generate the foamed fluid, whereactivating the fluid source and activating the foaming mechanism areperformed prior to delivering the foamed fluid to the wound dressing. Inparticular embodiments, the foaming mechanism comprises a mechanicalagitator. In certain embodiments, the mechanical agitator comprises oneor more rotating elements. The foaming mechanism may comprise a gasinjector in certain embodiments. In certain embodiments, the fluid(e.g., liquid) comprises one or more ingredients selected from the groupconsisting of: comprises sodium bicarbonate, citric acid, hydrogenperoxide, hypochlorous acid, sodium hypochlorite, sodium citrate,carbonic acid, potassium bicarbonate, potassium phosphate, and aceticacid.

In particular embodiments, a portion of the wound dressing isimpregnated with a foaming agent configured to foam a first fluid (e.g.,liquid), and where delivering a foamed fluid to a wound comprisesdelivering a first fluid to the wound dressing such that the first fluidreacts with the foaming agent to generate the foamed fluid. In certainembodiments, the foaming agent comprises one or more ingredientsselected from the group consisting of: sodium bicarbonate, citric acid,hydrogen peroxide, hypochlorous acid, sodium hypochlorite, sodiumcitrate, carbonic acid, potassium bicarbonate, potassium phosphate, andacetic acid. In particular embodiments, the first fluid comprises anacidic solution. In certain embodiments, the first fluid comprises oneor more ingredients selected from the group consisting of: citric acid,acetic acid, hypochlorous acid, ascorbic acid, benzoic acid, andlactated Ringer's solution.

In particular embodiments, the wound dressing comprises a drape coupledto the skin around the wound and a wound filler disposed between thedrape and wound, and the wound filler is impregnated with the foamingagent. In certain embodiments, the foamed fluid includes gas comprisingbetween 10 and 99 percent of the volume of the foamed fluid. In specificembodiments, the foamed fluid includes gas comprising between 20 and 90percent of the volume of the foamed fluid. In particular embodiments,the foamed fluid includes gas comprising between 40 and 80 percent ofthe volume of the foamed fluid. In still more particular embodiments,the foamed fluid includes gas comprising between 60 and 75 percent ofthe volume of the foamed fluid.

Certain embodiments comprise applying negative pressure to the woundthrough the wound dressing. In particular embodiments, applying negativepressure comprises activating a vacuum source coupled to the wounddressing. In specific embodiments, applying negative pressure isperformed after delivering the foamed fluid has stopped. In certainembodiments, applying negative pressure is performed simultaneously withdelivering the foamed fluid.

Particular embodiments comprise a wound treatment apparatus comprising:a vacuum source; a first fluid source configured to deliver a firstfluid (e.g., liquid); and a second fluid source configured to deliver asecond fluid (e.g., liquid); where the apparatus is configured to becoupled to a wound dressing such that the first and second fluid sourcesare activatable to combine the first and second fluids to generate afoamed fluid and deliver the foamed fluid to a wound. Certainembodiments comprise a wound dressing configured to be coupled to skinaround a wound of a patient such that the wound dressing covers thewound. In particular embodiments, the wound dressing comprises a drapeconfigured to be coupled to the skin around a wound, and a wound fillerconfigured to be disposed between the drape and the wound.

Certain embodiments include a wound treatment apparatus comprising: avacuum source; a fluid source configured to deliver a fluid (e.g.,liquid); and a foaming mechanism coupled to the fluid source andconfigured to foam the fluid, where the apparatus is configured to becoupled to a wound dressing such that the fluid source and foamingmechanism are activatable to deliver the foamed fluid to a wound.Specific embodiments comprise a wound dressing configured to be coupledto skin around a wound of a patient such that the wound dressing coversthe wound. In certain embodiments, the wound dressing comprises a drapeconfigured to be coupled to the skin around a wound of a patient and awound filler configured to be disposed between the drape and the wound.

Particular embodiments include a wound treatment apparatus comprising: avacuum source; and a fluid source configured to deliver a fluid (e.g.,liquid), where the apparatus is configured to be coupled to a wounddressing such that the fluid source is activatable to deliver a foamedfluid to a wound. In certain embodiments, the wound dressing comprises adrape configured to be coupled to the skin around a wound of a patientand a wound filler configured to be disposed between the drape and thewound, where the wound filler is impregnated with the foaming agent. Inspecific embodiments, the wound filler comprises a sterile porousmember. In certain embodiments, the foaming agent comprises one or moreingredients selected from the group consisting of: sodium bicarbonate,hydrogen peroxide, carbonic acid, and potassium bicarbonate.

Certain embodiments include a wound filler comprising: a sterile porousmember impregnated with a foaming agent configured to foam a fluid(e.g., liquid), where the porous member is configured to be disposedbetween a wound of a patient and a drape coupled to skin around thewound such that the drape covers the wound filler and the wound.

Details associated with the embodiments described above and others arepresented below.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings illustrate by way of example and not limitation.For the sake of brevity and clarity, every feature of a given structureis not always labeled in every figure in which that structure appears.Identical reference numbers do not necessarily indicate an identicalstructure. Rather, the same reference number may be used to indicate asimilar feature or a feature with similar functionality, as maynon-identical reference numbers.

FIG. 1 depicts a side view of an exemplary embodiment of a woundtreatment system according to the present disclosure.

FIG. 2 depicts a schematic block diagram of a first exemplary embodimentof a wound treatment system according to the present disclosure.

FIG. 3 depicts a schematic block diagram of a second exemplaryembodiment of a wound treatment system according to the presentdisclosure.

FIG. 4 depicts a schematic block diagram of a third exemplary embodimentof a wound treatment system according to the present disclosure.

FIG. 5 depicts a schematic block diagram of a fourth exemplaryembodiment of a wound treatment system according to the presentdisclosure.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The term “coupled” is defined as connected, although not necessarilydirectly, and not necessarily mechanically; two items that are “coupled”may be integral with each other. The terms “a” and “an” are defined asone or more unless this disclosure explicitly requires otherwise. Theterms “substantially,” “approximately,” and “about” are defined aslargely but not necessarily wholly what is specified, as understood by aperson of ordinary skill in the art.

The terms “comprise” (and any form of comprise, such as “comprises” and“comprising”), “have” (and any form of have, such as “has” and“having”), “include” (and any form of include, such as “includes” and“including”) and “contain” (and any form of contain, such as “contains”and “containing”) are open-ended linking verbs. As a result, a woundtreatment method that “comprises,” “has,” “includes” or “contains” oneor more steps possesses those one or more steps, but is not limited topossessing only those one or more steps Likewise, a wound treatmentsystem that “comprises,” “has,” “includes” or “contains” one or moreelements possesses those one or more elements, but is not limited topossessing only those elements.

Further, a device, apparatus or structure that is configured in acertain way is configured in at least that way, but it can also beconfigured in other ways than those specifically described.

Referring now to the drawings, and more particularly to FIG. 1, showntherein is an embodiment of one of the present wound treatment system10. In the embodiment shown, system 10 comprises a wound-treatmentapparatus 14, and a wound dressing 18. In the embodiment shown,apparatus 14 is coupled to wound dressing 18 by a conduit 22. As shown,dressing 18 is configured to be coupled to (and is shown coupled to) awound 26 of a patient 30. More particularly, in the embodiment shown,dressing 18 comprises a wound insert 34 and a drape 38. As shown, woundinsert 34 is configured to be positioned (and is shown positioned) onwound 26 (e.g., on or adjacent to wound surface 42), and/or drape 38 isconfigured to be coupled to (and is shown coupled to) skin 46 of thepatient adjacent to wound 26 such that drape 38 covers wound insert 34and wound 26, and forms a chamber 50 between drape 38 and wound 26(e.g., wound surface 42).

Apparatus 14 can comprise, for example, a vacuum source configured to beactuatable (and/or actuated) to apply negative pressure (e.g., viaconduit 22) to wound dressing 18, a fluid source configured to beactuatable (and/or actuated) to deliver (e.g., via conduit 22) a fluid(e.g., an installation fluid such as a medicinal fluid, antibacterialfluid, irrigation fluid, and/or the like) to wound dressing 18. System10 can be implemented and/or actuated and/or coupled to patient 30 inany of various configurations and/or methods similar to those describedin the prior art, including for example U.S. Pat. No. 7,611,500, thedisclosure of which is incorporated here in its entirety. Additionally,various wound therapy systems and components are commercially availablethrough and/or from KCI USA, Inc. of San Antonio, Tex., U.S.A. and/orits subsidiary companies such as in its V.A.C.® and SensaTRAC® productlines, as discussed further below.

Conduit 22 can comprise a single lumen conduit (e.g., switched between avacuum source and/or a fluid source and apparatus 14), or can comprisemultiple single-lumen conduits or a multi-lumen conduit such that, forexample, fluid can be delivered and/or negative pressure can be appliedto wound dressing 18 individually and/or simultaneously. Additionally,conduit 22 can comprise, for example, a first lumen for the applicationof negative pressure and/or fluid delivery, and at least one additionallumen for coupling to pressure sensor(s) to sense pressure or negativepressure between drape 38 and surface 42. In some embodiments, conduit22 can comprise multiple lumens (e.g., as in a single conduit with acentral lumen for application of negative pressure and/or fluiddelivery, and one or more peripheral lumens disposed adjacent or aroundthe central lumen such that the peripheral lumens can be coupled to apressure sensor to sense a pressure or negative pressure between drape38 and surface 42 (e.g. in space 50). The lumens may be arranged with acentral lumen and other lumens disposed radially around the centrallumen, or in other suitable arrangements. The lumens may also beprovided in separate conduits. In the embodiment shown, system 10further comprises a wound dressing connection pad 54 configured to becoupled (and is shown coupled) to conduit 22. One example of a suitableconnection pad 54 is the “V.A.C. T.R.A.C.® Pad,” commercially availablefrom KCI. One example of a suitable drape 38 includes the “V.A.C.®Drape” commercially available from KCI. Another example of a connectionpad 54 is disclosed in U.S. patent application Ser. No. 11/702,822,incorporated above.

One example of a suitable drape 38 includes the “V.A.C.® Drape”commercially available from KCI USA, Inc. (and its affiliates) of SanAntonio, Tex., U.S.A.

Typical open-celled foam wound fillers generally do not wick ordistribute fluids effectively. An effective wicking wound filler isdesirable where fluids are instilled into a wound for varioustherapeutic effects (e.g., antiseptics and antibiotics). By reducing thepore size of such foams (and also by incorporating hydrophilic coatings,or using inherently hydrophilic foams), the wicking ability may beimproved, but smaller pores can attract the risk of increased blockingby wound fluid borne agents and particulates. Utilizing voids (e.g.,holes or channels) in the foam can help to reduce the effects of poormanifolding due to pore blocking, but current processes limit the lengthof void that may be created in the foam.

Exemplary embodiments of the present disclosure may utilize wound insert34 comprising an open-celled foam (which may also be reticulated) thatis configured to exhibit hydrophilic properties. In contrast tohydrophobic foams traditionally used with NPWT systems and methods, thehydrophilic properties of wound insert 34 improve the movement of fluids(e.g., liquids, such as, instillation fluids, body fluids, exudate, andthe like) through the wound insert, such that fluid is encouraged totravel through wound insert 34 rather than around the wound insert 34 oradjacent to the interface between drape 38 and skin 46.

With traditional hydrophobic wound inserts, fluid typically travels in apath such that the fluid minimizes contact with the foam, and such thatfluid is repelled from the foam and may generate pressure between thefoam and interface between drape 38 and skin 46. In this way withhydrophobic wound inserts, drape 38 may be forced away from skin 46about the perimeter of wound 26. In this way, with traditionalhydrophobic wound inserts, very little of the fluid is retained ortransferred through the foam itself. Because fluid may be forced outwardfrom the hydrophobic wound insert, the fluid can generate a positivepressure at the interface between the drape and skin adjacent to thewound. This can lead to a ballooning effect which can stress theinterface between drape adjacent skin, and can lead to failure of theadhesive generally used to couple the drape to the skin.

However, with hydrophilic wound inserts 34, fluid can travel through thewound insert 34 (e.g., evenly dispersed throughout wound insert 34),thus decreasing the positive pressure within chamber 50 and at theinterface between drape 38 and skin 46. As such, with hydrophilic woundinserts 34, fluid typically will not pool at the interface between drape38 and skin 46 as quickly, such that the integrity of adhesive or thelike coupling drape 38 to skin 46 is maintained longer and permits moredurable adhesion between drape 38 and 46. In this way, wound dressings18 comprising drape 38 and wound insert 34 are typically more durableand/or less prone to failure.

As illustrated in the exemplary embodiment of FIG. 1, wound dressings 18comprise a wound insert 34 configured to be positioned on a wound 26(e.g., wound surface 42) of a patient (e.g., 30), the wound insertcomprising an open-celled foam (which may also be reticulated)configured to exhibit hydrophilic properties; and a drape 38 configuredto be coupled to skin 46 of the patient adjacent the wound such thatdrape 38 covers wound insert 34 and wound 26 and forms chamber 50between the drape and the wound. Wound insert 34 can comprise anysuitable material and/or combination of materials that permit woundinsert 34 to exhibit hydrophilic properties. For example, in someembodiments, wound insert 34 comprises an open celled hydrophobic foam(which may also be reticulated) that is coated with a hydrophiliccoating (e.g., a coating configured to cause the hydrophobic foam toexhibit hydrophilic properties). In some embodiments, the hydrophiliccoating comprises polyvinyl alcohol (PVOH), plasticizer (e.g., triethylcitrate, or the like), hydrophilic polyurethane, gelatin, hyaluronicacid, heparin, and/or any other suitable coating configured to cause thecoated hydrophobic foam to exhibit hydrophilic properties.

Embodiments of the present wound treatment methods may be betterunderstood with reference to FIG. 2. FIG. 2 depicts a schematic blockdiagram of one embodiment of system 10. In the embodiment shown, wounddressing 18 is coupled to apparatus 14, and apparatus 14 comprises avacuum source 200 (e.g., a vacuum pump and/or the like) coupled to acanister 204 (e.g., configured to receive exudate and or the like fromwound dressing 18) by way of a conduit 208. In the embodiment shown,apparatus 14 further comprises: a pressure sensor 212 having a firstpressure transducer 216 coupled to conduit 208 by way of conduit 220and/or tee-fitting 224, and a second pressure transducer 228 coupled tocanister 204 and/or wound dressing 18 by way of conduit 232. Pressuresensor 212 is configured to sense the negative pressure in wounddressing 18, and/or any of the various lumens (e.g., within conduits)coupled to wound dressing 18, pressure sensor 212, and/or vacuum source200.

In the embodiment shown, apparatus 14 further comprises a pressurerelease valve 236 coupled to conduit 232. Further, in the embodimentshown, canister 204 and vacuum source 200 are coupled to wound dressing18 by way of conduit 240. In the embodiment shown canister 204 cancomprise a filter 244 at or near an outlet of canister 204 to preventliquid or solid particles from entering conduit 208. Filter 244 cancomprise, for example, a bacterial filter that is hydrophobic and/orlipophilic such that aqueous and/or oily liquids will bead on thesurface of the filter. Apparatus 14 is typically configured such thatduring operation vacuum source 200 will provide sufficient airflowthrough filter 244 that the pressure drop across filter 244 is notsubstantial (e.g., such that the pressure drop will not substantiallyinterfere with the application of negative pressure from wound dressing18 from vacuum source 200).

In the embodiment shown, apparatus 14 further comprises a fluid source248 coupled to wound dressing 18 by way of a conduit 252 that is coupledto conduit 240 such as, for example, by way of a tee- or other suitablefitting 256. In some embodiments, tee fitting 256 can comprise a switchvalve and the like such that communication can be selectively permittedbetween wound dressing 18 and vacuum source 200, or between wounddressing 18 and fluid source 248. In some embodiments apparatus 14comprises only one of vacuum source 200 and fluid source 248. Forembodiments of apparatus 14 that comprise only fluid source 248,canister 204 and/or pressure sensor 212 can also be omitted. In variousembodiments, such as the one shown, conduit 232 and/or conduit 240and/or conduit 252 can be combined and/or comprised in a singlemulti-lumen conduit, such as is described above with reference to FIG.1.

In various embodiments, such as the one shown in FIG. 2, apparatus 14can be configured such that as soon as the liquid in the canisterreaches a level where filter 244 is occluded, a much-increased negative(or subatmospheric) pressure occurs in conduit 208 and is sensed bytransducer 216. Transducer 216 can be connected to circuitry thatinterprets such a pressure change as a filled canister and signals thisby means of a message on a visible and/or audible alarm that canister204 requires emptying and/or replacement, and/or that automaticallyshuts off or disables vacuum source 200.

Apparatus 14 can also be configured to apply negative (orsubatmospheric) pressure (e.g., continuously, intermittently, and/orperiodically) to the wound site, and/or such that pressure relief valve236 enables pressure at the wound site to be brought to atmosphericpressure rapidly. Thus, if apparatus 14 is programmed, for example, torelieve pressure at ten-minute intervals, at these intervals pressurerelief valve 236 can open for a specified period, allow the pressure toequalize at the wound site, and then close to restore the negativepressure. It will be appreciated that when constant negative pressure isbeing applied to the wound site, valve 236 remains closed to preventleakage to or from atmosphere. In this state, it is possible to maintainnegative pressure at the wound site without running and/or operatingpump 200 continuously, but only from time to time or periodically, tomaintain a desired level of negative pressure (i.e. a desired pressurebelow atmospheric pressure), which is sensed by transducer 216. Thissaves power and enables the appliance to operate for long periods on itsbattery power supply.

In specific embodiments, the fluid provided to a wound dressing maycomprise a foamed fluid. Referring now to FIG. 3, a schematic diagram ofa wound treatment system 310 comprises a wound dressing 318 and a woundtreatment apparatus 314 coupled via a conduit 322. Similar topreviously-described embodiments, apparatus 314 may comprise a vacuumsource configured to apply intermittent negative (or subatmospheric)pressure to the wound dressing 318. In this exemplary embodiment, afirst fluid source 348 comprising a first fluid and a second fluidsource 349 comprising a second fluid are coupled to wound dressing 318via conduits 340, 341, 342 and coupling member or combiner fitting 346.In exemplary embodiments, first and second fluids from first fluidsource 348 and second fluid source 349 are configured to produce afoamed fluid when mixed. In related exemplary embodiments, first andsecond fluids from first and second fluid sources 348, 349 are deliveredseparately to wound dressing 318 and mixed within wound dressing 318 toproduce a foamed fluid. In certain embodiments, first fluid source 348may comprise a first fluid that is an acidic solution, while secondfluid source 349 may comprise a second fluid that is a basic solution.

In specific exemplary embodiments, first fluid source 348 may comprisecitric acid, acetic acid, hypochlorous acid, ascorbic acid, and/orbenzoic acid. Second fluid source 349, in exemplary embodiments, maycomprise a basic or bicarbonate solution. Non-limiting examples of asecond fluid from second fluid source 349 include sodium bicarbonate,hydrogen peroxide and carbonic acid. In particular exemplaryembodiments, the first and/or second fluids may comprise a surfactantconfigured to stabilize the foamed fluid. In exemplary embodiments, thefoamed fluid includes gas comprising between 10 and 99 percent (e.g.,between 20 and 90, and/or between 40 and 80 percent) of the volume ofthe foamed fluid. For example, in some embodiments, the foamed fluidincludes gas comprising between 60 and 75 percent of the volume of thefoamed fluid such that the foamed fluid contains substantially lessliquid than a fluid comprising only liquid, but still contains enoughliquid to be effective for cleaning, debriding, and/or disinfecting awound.

During operation of wound treatment system 310, first fluid source 348and second fluid source 349 can be activated to deliver first and secondfluids, respectively, that are drawn into conduit 342 and mixed togetherto produce a foamed fluid that enters wound dressing 318. In specificexemplary embodiments, wound dressing 318 may be vented to allow excessgas to escape (e.g., by opening pressure-relief valve 236, or byproviding a one-way valve in drape 38).

Delivering a foamed instilled fluid can increase its coverage in thewound by reducing the amount of fluid required to fill the wound andwound dressing 318. In particular embodiments, wound dressing 318 maycomprise distribution channels to distribute the foamed fluid toparticular regions. Although the foamed instill fluid is effectivelydiluted with gas, as the foam collapses at the wound surface the resultis efficient coverage, particularly where surfactants are used.

In certain embodiments, the use of foamed fluid can provide additionalversatility for the frequency and/or duration of the liquidinstillation. For example, more frequent fluid instills, or even acontinuous instillation, may be employed to present successive waves offoam to the wound surface without increasing the total volume ofinstillation fluid (as compared to methods using non-foamed liquids).

In certain exemplary embodiments, the foam is self-supporting and willrapidly collapse under the application of negative pressure. In otherembodiments, the foam is substantially stable (will resist collapsing)under the application of negative pressure for at least a period of timesufficient to draw foam into a wound dressing by application of negativepressure without collapsing the foam. The compressible nature of thefoam can allow slight overfilling of the wound without placing unduepressure on the dressing, which can reduce the occurrence of leaks. Theapplication of a vacuum during instillation, the compressible nature ofthe foam, and/or the use of suitable surfactants can enable the foamedfluid to more effectively fill tortuous cavities (as compared tonon-foamed fluids). Although high volumes of foamed fluid may be used toinstill a wound, the foamed fluid can be withdrawn to a canister (andcollapsed, if not collapsed in or as drawn from the wound), therebyreducing the volume of used liquid (e.g., which must be disposed of).

In other embodiments, foamed instillation fluid may be generated via amechanical apparatus. Referring now to FIG. 4, a wound treatment system410 comprises a wound dressing 418 and a wound treatment apparatus 414coupled via a conduit 422. Similar to previously-described embodiments,apparatus 414 may comprise a vacuum source configured to applyintermittent negative (or subatmospheric) pressure to the wound dressing418. In this exemplary embodiment, a first fluid source 448 comprising afirst fluid is coupled to wound dressing 418 via a conduit 442. In theexemplary embodiment shown, a foaming mechanism 449 (e.g. a mechanicalagitator), is used to generate a foamed fluid from the first fluid(e.g., liquid), which can be instilled into wound dressing 418 aspreviously described. In particular exemplary embodiments foamingmechanism 449 may comprise one or more rotating elements that generate afoam when placed in contact with the first fluid. In specific exemplaryembodiments, foaming mechanism 449 may comprise an electric motorconfigured to rotate a shaft with paddles or other shaft extensions thatcontact the first fluid during operation.

In still other embodiments, foamed instillation fluid may be generatedvia a different foaming mechanism. Referring now to FIG. 5, a woundtreatment system 510 comprises a wound dressing 518 and a woundtreatment apparatus 514 coupled via a conduit 522. Similar topreviously-described embodiments, apparatus 514 may comprise a vacuumsource configured to apply intermittent negative (or subatmospheric)pressure to the wound dressing 518. In this exemplary embodiment, afirst fluid source 548 comprising a first fluid is coupled to wounddressing 518 via a conduit 542. In the illustrated exemplary embodiment,a foaming mechanism 549 (e.g. a gas injector) is used to inject a gasinto the first fluid (e.g., liquid) and generate a foamed fluid that canbe instilled into wound dressing 518 as previously described. Inspecific exemplary embodiments, foaming mechanism 549 may comprise areservoir of pressurized air and a nozzle configured to direct thepressurized air into the first fluid.

Still other embodiments may comprise different methods or systems forgenerating a foamed instill fluid. For example, instead of reactiveliquids or mechanically generated foam, certain embodiments may use lowboiling point liquids, emulsions, or dispersions that may be deliveredto a wound and generate foam upon an increase in temperature. Forexample, in some embodiments, a low-boiling-point liquid is addedanother liquid (e.g., water, saline, etc.) such that upon boiling, thelow-boiling-point liquid will foam the other liquid. In certainexemplary embodiments, an increase in temperature sufficient to causeboiling of the low-boiling-point liquid can be supplied by the bodytemperature of the patient. In other exemplary embodiments, the increasein temperature may be provided by an external heater.

In particular exemplary embodiments, the wound dressing may act as acatalyst on given instilled liquids generating gases and/or createfoamed liquids. For example, certain metals on contact with peroxidesand hydroperoxides will liberate oxygen. Similar processes may beemployed to liberate other gases such as carbon dioxide for example. Incertain embodiments, the wound dressing may comprise or be coated with afoaming agent that when exposed to a dilute acid will liberate a gas(e.g., carbon dioxide). In certain embodiments, the foaming agent maycomprise sodium bicarbonate, potassium bicarbonate, and carbonic acid.

In particular embodiments, the wound dressing comprises a drape coupledto the skin around the wound and a wound filler disposed between thedrape and wound, and the wound filler can be impregnated with thefoaming agent.

In particular embodiments, the gas generated may be a wound disinfectingagent (e.g., an antibiotic or antiseptic). In certain exemplaryembodiments, abrasive particulates may be added to the foam to provide ascouring effect and help debride the wound.

Particular exemplary embodiments utilize closed-cell foams that producelittle or no granulation under NPWT, such as, for example, alone or incombination with open-cell foams. This low or no granulation effect maybe employed in wounds were metal components (e.g. bolts, plates, etc.)are employed and granulation is not desired. This can protect the metalcomponents from the granulation process by applying foam to them, suchthat, for example, the closed-cell foam directs fluids (e.g., foamedfluids) around the closed-cell foam to be applied to the wound aroundsuch metal components. In exemplary embodiments, the foam can moreefficiently cover these metal structures than typical methods that usefilms or gels.

Exemplary embodiments also comprise wound treatment methods utilizingthe previously-described systems. In specific exemplary embodiments, thefoamed fluid is generated (e.g., by one or more of the previouslydescribed methods or systems) and delivered to a wound of a patientthrough a wound dressing that is coupled to the skin around the wound.

The various illustrative embodiments of devices, systems, and methodsdescribed herein are not intended to be limited to the particular formsdisclosed. Rather, they include all modifications, equivalents, andalternatives falling within the scope of the claims.

The claims are not intended to include, and should not be interpreted toinclude, means-plus- or step-plus-function limitations, unless such alimitation is explicitly recited in a given claim using the phrase(s)“means for” or “step for,” respectively.

It will be understood that the benefits and advantages described abovemay relate to one embodiment or may relate to several embodiments. Itwill further be understood that reference to ‘an’ item refers to one ormore of those items, unless otherwise specified.

The steps of the methods described herein may be carried out in anysuitable order, or simultaneously where appropriate.

Where appropriate, aspects of any of the examples described above may becombined with aspects of any of the other examples described to formfurther examples having comparable or different properties andaddressing the same or different problems.

It will be understood that the above description of preferredembodiments is given by way of example only and that variousmodifications may be made by those skilled in the art. The abovespecification, examples and data provide a complete description of thestructure and use of exemplary embodiments. Although various embodimentshave been described above with a certain degree of particularity, orwith reference to one or more individual embodiments, those skilled inthe art could make numerous alterations to the disclosed embodimentswithout departing from the scope of this invention.

1.-10. (canceled)
 11. A wound treatment apparatus comprising: a drapefor securing to the skin of a patient around a wound, thereby creating aspace between the wound and the drape; a wound filler for placement onthe wound in the space between the wound and the drape; a vacuum sourcein fluid communication with the space between the wound and the drapefor applying a negative pressure to that space; and a source of liquidin fluid communication with the space between the wound; where the woundfiller comprises a foaming agent for forming a foam when liquid from theliquid source contacts the foaming agent.
 12. The wound treatmentapparatus of claim 11 where the foaming agent comprises one or moreingredients selected from the group consisting of: sodium bicarbonate,hydrogen peroxide, carbonic acid, and potassium bicarbonate.
 13. A woundtreatment method comprising: delivering a foamed fluid to a wound of apatient through a wound dressing covering the wound and coupled to skinaround the wound.
 14. The method of claim 13, further comprising:combining a first fluid and a second fluid to generate the foamed fluid.15. The method of claim 14, where the first fluid comprises an acidicsolution, and the second fluid comprises a basic solution.
 16. Themethod of claim 15, where at least one of the first fluid and the secondfluid comprises a surfactant configured to stabilize the foamed fluid.17. The method of claim 14, where the first fluid comprises one or moreingredients selected from the group consisting of: citric acid, aceticacid, hypochlorous acid, ascorbic acid, and benzoic acid.
 18. The methodof claim 14, where the second fluid comprises one or more ingredientsselected from the group consisting of: sodium bicarbonate, carbonicacid, and potassium citrate.
 19. The method of claim 14, where the firstfluid and the second fluid are delivered to the wound dressing such thatthe first fluid and the second fluid combine to generate the foamedfluid in the wound dressing.
 20. The method of claim 13, furthercomprising: activating a fluid source to deliver a fluid to a foamingmechanism; activating a foaming mechanism to foam the first fluid togenerate the foamed fluid; where activating the fluid source andactivating the foaming mechanism are performed prior to delivering thefoamed fluid to the wound dressing.
 21. The method of claim 13, where aportion of the wound dressing is impregnated with a foaming agentconfigured to foam a first fluid and where delivering the foamed fluidto a wound comprises delivering a first fluid to the wound dressing suchthat the first fluid reacts with the foaming agent to generate thefoamed fluid.
 22. The method of claim 21, where the foaming agentcomprises one or more ingredients selected from the group consisting of:sodium bicarbonate, hydrogen peroxide, carbonic acid, and potassiumbicarbonate.
 23. The method of claim 13, where the foamed fluid includesgas comprising between 60 and 75 percent of the volume of the foamedfluid.
 24. The method of claim 13, further comprising: applying negativepressure to the wound through the wound dressing.
 25. The method ofclaim 24, where applying negative pressure is performed simultaneouslywith delivering the foamed fluid.
 26. A wound filler comprising: aporous member impregnated with a foaming agent configured to foam afluid; where the porous member is configured to be disposed between awound of a patient and a drape coupled to skin around the wound suchthat the drape covers the wound filler and the wound.
 27. The woundfiller of claim 26, where the foaming agent comprises one or moreingredients selected from the group consisting of: sodium bicarbonate,hydrogen peroxide, carbonic acid, and potassium bicarbonate.